Photographic printers typically include a combination of several basic components for the printing process. A negative feed and holder assembly typically operates to store and transport an elongated strip of negative film images. The negative holder assembly also operates to orient a single selected negative image in a position for use in the printing process. A photographic paper feed and holder assembly typically operates to store and transport an elongated web of light sensitive photographic paper. The paper holder assembly also operates to orient a selected area of the web in a position for use in the printing process. A source of light operates to project light through the selected negative image onto the photographic paper. A lens, or group of lenses, positioned between the negative and photographic paper operates to focus and/or transmit the light onto the photographic paper to produce the desired image, or group of images. These basic components are typically housed in a framework that allows an operator to conveniently control the printing process.
Photographic printers typically take the form of either a "proof" or "package" photographic printer arrangement. As a basic distinction, a "proof" printer is adapted to print individual photographic prints from a given negative, while a "package" printer is adapted to print 11 .times.14 sheets having groups of various size photographic prints from a single negative. Using an exposure of a school student as an example, a "proof" printer would initially be used to print a single image, or a series of images at various exposure levels, of the child for use in initially reviewing the quality of the print. A "package" printer would thereafter be used to produce the multi-image sheets of photographs that parents purchase each year of their children's school pictures.
Operators of photographic printers are generally confronted with the task of exposing various size photographic images from various size negative images. Generally speaking, multiple lenses are needed to produce multiple size photographic images from various size negatives. U.S. Pat. No. 3,951,545, issued on Apr. 20, 1976, discloses a package printer arrangement having a lens carrier assembly housing a plurality of lens boards mounted in a stacked and spaced relationship to one another. A series of external plungers operate to slide the lens boards into operative positions. To accommodate for printing from different size negatives, this reference discloses the manual replacement of a singe lens board or the entire lens carrier assembly. U.S. Pat. No. 4,583,845, issued on Apr. 22, 1986, discloses a printer arrangement having a lens assembly housing a carousel rotatably supporting a plurality of lens assemblies about a series of plungers. This reference, commonly assigned to the same entity as the first reference discussed, specifically attempts to increase the number of lens configurations available as disclosed in the first prior art reference without requiring a manual substitution of one lens assembly for another. These devices require multiple actuators, drive assemblies, support units, and biasing devices to operate. This multiplicity of components is costly to manufacture, repair, and maintain. Further, the lens assemblies of the prior art are spring biased toward the inoperative position. This biasing arrangement produces various impact forces on the equipment during operation of the devices that may adversely affect the continued performance of the equipment.
Thus, there is a need in the industry to provide an efficient and inexpensive mechanism by which individual lenses, or multiple lens units, may be aligned along the optical center-line of a photographic printer to allow for the exposure of a variety of size photographic prints from a variety of sizes of photographic negative images.